1 /*
2  * System Control and Power Interface (SCPI) based CPUFreq Interface driver
3  *
4  * Copyright (C) 2015 ARM Ltd.
5  * Sudeep Holla <sudeep.holla@arm.com>
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License version 2 as
9  * published by the Free Software Foundation.
10  *
11  * This program is distributed "as is" WITHOUT ANY WARRANTY of any
12  * kind, whether express or implied; without even the implied warranty
13  * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14  * GNU General Public License for more details.
15  */
16 
17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
18 
19 #include <linux/clk.h>
20 #include <linux/cpu.h>
21 #include <linux/cpufreq.h>
22 #include <linux/cpumask.h>
23 #include <linux/export.h>
24 #include <linux/module.h>
25 #include <linux/of_platform.h>
26 #include <linux/pm_opp.h>
27 #include <linux/scpi_protocol.h>
28 #include <linux/slab.h>
29 #include <linux/types.h>
30 
31 struct scpi_data {
32 	struct clk *clk;
33 	struct device *cpu_dev;
34 };
35 
36 static struct scpi_ops *scpi_ops;
37 
38 static unsigned int scpi_cpufreq_get_rate(unsigned int cpu)
39 {
40 	struct cpufreq_policy *policy = cpufreq_cpu_get_raw(cpu);
41 	struct scpi_data *priv = policy->driver_data;
42 	unsigned long rate = clk_get_rate(priv->clk);
43 
44 	return rate / 1000;
45 }
46 
47 static int
48 scpi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
49 {
50 	u64 rate = policy->freq_table[index].frequency * 1000;
51 	struct scpi_data *priv = policy->driver_data;
52 	int ret;
53 
54 	ret = clk_set_rate(priv->clk, rate);
55 
56 	if (ret)
57 		return ret;
58 
59 	if (clk_get_rate(priv->clk) != rate)
60 		return -EIO;
61 
62 	return 0;
63 }
64 
65 static int
66 scpi_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpumask)
67 {
68 	int cpu, domain, tdomain;
69 	struct device *tcpu_dev;
70 
71 	domain = scpi_ops->device_domain_id(cpu_dev);
72 	if (domain < 0)
73 		return domain;
74 
75 	for_each_possible_cpu(cpu) {
76 		if (cpu == cpu_dev->id)
77 			continue;
78 
79 		tcpu_dev = get_cpu_device(cpu);
80 		if (!tcpu_dev)
81 			continue;
82 
83 		tdomain = scpi_ops->device_domain_id(tcpu_dev);
84 		if (tdomain == domain)
85 			cpumask_set_cpu(cpu, cpumask);
86 	}
87 
88 	return 0;
89 }
90 
91 static int scpi_cpufreq_init(struct cpufreq_policy *policy)
92 {
93 	int ret;
94 	unsigned int latency;
95 	struct device *cpu_dev;
96 	struct scpi_data *priv;
97 	struct cpufreq_frequency_table *freq_table;
98 
99 	cpu_dev = get_cpu_device(policy->cpu);
100 	if (!cpu_dev) {
101 		pr_err("failed to get cpu%d device\n", policy->cpu);
102 		return -ENODEV;
103 	}
104 
105 	ret = scpi_ops->add_opps_to_device(cpu_dev);
106 	if (ret) {
107 		dev_warn(cpu_dev, "failed to add opps to the device\n");
108 		return ret;
109 	}
110 
111 	ret = scpi_get_sharing_cpus(cpu_dev, policy->cpus);
112 	if (ret) {
113 		dev_warn(cpu_dev, "failed to get sharing cpumask\n");
114 		return ret;
115 	}
116 
117 	ret = dev_pm_opp_set_sharing_cpus(cpu_dev, policy->cpus);
118 	if (ret) {
119 		dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n",
120 			__func__, ret);
121 		return ret;
122 	}
123 
124 	ret = dev_pm_opp_get_opp_count(cpu_dev);
125 	if (ret <= 0) {
126 		dev_dbg(cpu_dev, "OPP table is not ready, deferring probe\n");
127 		ret = -EPROBE_DEFER;
128 		goto out_free_opp;
129 	}
130 
131 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
132 	if (!priv) {
133 		ret = -ENOMEM;
134 		goto out_free_opp;
135 	}
136 
137 	ret = dev_pm_opp_init_cpufreq_table(cpu_dev, &freq_table);
138 	if (ret) {
139 		dev_err(cpu_dev, "failed to init cpufreq table: %d\n", ret);
140 		goto out_free_priv;
141 	}
142 
143 	priv->cpu_dev = cpu_dev;
144 	priv->clk = clk_get(cpu_dev, NULL);
145 	if (IS_ERR(priv->clk)) {
146 		dev_err(cpu_dev, "%s: Failed to get clk for cpu: %d\n",
147 			__func__, cpu_dev->id);
148 		ret = PTR_ERR(priv->clk);
149 		goto out_free_cpufreq_table;
150 	}
151 
152 	policy->driver_data = priv;
153 	policy->freq_table = freq_table;
154 
155 	/* scpi allows DVFS request for any domain from any CPU */
156 	policy->dvfs_possible_from_any_cpu = true;
157 
158 	latency = scpi_ops->get_transition_latency(cpu_dev);
159 	if (!latency)
160 		latency = CPUFREQ_ETERNAL;
161 
162 	policy->cpuinfo.transition_latency = latency;
163 
164 	policy->fast_switch_possible = false;
165 
166 	dev_pm_opp_of_register_em(cpu_dev, policy->cpus);
167 
168 	return 0;
169 
170 out_free_cpufreq_table:
171 	dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);
172 out_free_priv:
173 	kfree(priv);
174 out_free_opp:
175 	dev_pm_opp_remove_all_dynamic(cpu_dev);
176 
177 	return ret;
178 }
179 
180 static int scpi_cpufreq_exit(struct cpufreq_policy *policy)
181 {
182 	struct scpi_data *priv = policy->driver_data;
183 
184 	clk_put(priv->clk);
185 	dev_pm_opp_free_cpufreq_table(priv->cpu_dev, &policy->freq_table);
186 	dev_pm_opp_remove_all_dynamic(priv->cpu_dev);
187 	kfree(priv);
188 
189 	return 0;
190 }
191 
192 static struct cpufreq_driver scpi_cpufreq_driver = {
193 	.name	= "scpi-cpufreq",
194 	.flags	= CPUFREQ_STICKY | CPUFREQ_HAVE_GOVERNOR_PER_POLICY |
195 		  CPUFREQ_NEED_INITIAL_FREQ_CHECK |
196 		  CPUFREQ_IS_COOLING_DEV,
197 	.verify	= cpufreq_generic_frequency_table_verify,
198 	.attr	= cpufreq_generic_attr,
199 	.get	= scpi_cpufreq_get_rate,
200 	.init	= scpi_cpufreq_init,
201 	.exit	= scpi_cpufreq_exit,
202 	.target_index	= scpi_cpufreq_set_target,
203 };
204 
205 static int scpi_cpufreq_probe(struct platform_device *pdev)
206 {
207 	int ret;
208 
209 	scpi_ops = get_scpi_ops();
210 	if (!scpi_ops)
211 		return -EIO;
212 
213 	ret = cpufreq_register_driver(&scpi_cpufreq_driver);
214 	if (ret)
215 		dev_err(&pdev->dev, "%s: registering cpufreq failed, err: %d\n",
216 			__func__, ret);
217 	return ret;
218 }
219 
220 static int scpi_cpufreq_remove(struct platform_device *pdev)
221 {
222 	cpufreq_unregister_driver(&scpi_cpufreq_driver);
223 	scpi_ops = NULL;
224 	return 0;
225 }
226 
227 static struct platform_driver scpi_cpufreq_platdrv = {
228 	.driver = {
229 		.name	= "scpi-cpufreq",
230 	},
231 	.probe		= scpi_cpufreq_probe,
232 	.remove		= scpi_cpufreq_remove,
233 };
234 module_platform_driver(scpi_cpufreq_platdrv);
235 
236 MODULE_ALIAS("platform:scpi-cpufreq");
237 MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
238 MODULE_DESCRIPTION("ARM SCPI CPUFreq interface driver");
239 MODULE_LICENSE("GPL v2");
240